Leaky dam in region spawns repair project

PIEDMONT, Mo. -- The U.S. Corps of Engineers wants to build a $90 million concrete wall to halt seepage that is threatening a Southeast Missouri dam.

The source of concern is the Clearwater Lake Dam near Piedmont, which opened in 1948 to control flooding along the Black River. Corps officials are worried that another major flood like those in 1993 and 1995 could cause the dam to break.

"An embankment failure during a large flood event could cause up to $200 million in damage and up to 369 deaths," corps project manager Mark Brightwell of Little Rock, Ark., said during a public meeting Monday in nearby Poplar Bluff.

To fix the problem, the corps has proposed a 230-foot-deep subsurface concrete cutoff wall that would be built along the centerline of the 4,300-foot dam at a cost of about $90 million.

Brightwell said seepage problems have existed for several years. In January 2003, a sinkhole was discovered near the center of the dam.

"This sinkhole, as well as subsequent geophysical and subsurface investigations, calls into question the integrity of the entire dam embankment and clay core," Brightwell said.

An environmental assessment by the corps indicates construction of the concrete wall would not hurt the environment, officials said.

The project would mean the closing of Route HH, which crosses the dam, during the three-year construction period, Brightwell said. But both Randall Devenport, the corps' park ranger at Clearwater Lake, and Missouri Department of Transportation area engineer Lindell Huskey want the road to remain open.

Brightwell said the corps would consider other options, such as limiting the highway to one-lane traffic.